Pipe clamp thermocouple

ABSTRACT

A thermocouple assembly for measuring the temperature of a pipe, comprises a pipe clamp having a pair of dissimilar metal strips mounted therein to contact a pipe held in the pipe clamp. A thermocouple reading instrument is connected to the metal strips to indicate the temperature of the pipe.

BACKGROUND OF THE INVENTION

This invention relates to measuring the temperature of fluids in a pipe.Refrigeration and air conditioning technicians need temperatures offluids in pipes for proper adjustment. If they can get the temperatureof the pipe itself, in most cases that's good enough.

Many companies supply products that include various mechanisms andtechnologies to get the temperature of the pipe. These include beadedthermocouples with a Velcro strap, thermistors in a ‘clothespin’ styleclamp, and several different methods of using thermocouples in a plasticclamp.

There are primarily two thermocouple techniques used for pipe clamps.One is to weld the individual thermocouples to a metal plate, and thenmechanically press the metal plate against the pipe. The thermocoupledelivers a voltage proportional to somewhere between that delivered bythe two junctions to the plate.

To accommodate a wider variety of pipes, the plate has to be “V” or “U”shaped. If the plate is a “V,” at best there are two line-shapedcontacts. Most of the contacting force for big pipes is on one plate,while the contacting force for the little pipe is on the other plate,with the varying force creating thermal conducting problems, sinceconductivity varies with the force applied.

Beyond that, the impediments to speed and accuracy with this techniqueare many, including that the plate dissipates heat to the environmenteasily due to big area of contact with ambient air. The contact pointwith the plate may be far from the thermocouple junctions; the contactspot changes as the jaws of the clamp get wider; the contact spot sizemay be small; the plate may absorb a lot of heat; the force between thecontact plate and the pipe vary causing varying thermal conductance andthe plate mounting mechanism (usually tabs) offers a path for heat tothe environment. In addition, with any kind of clamp that has pivotingarms (like scissors or salad grabbers) the angle of the jaws vary as theclamp opens and closes, causing contact spot variability.

The other technique is to push a thermocouple junction made of ribbonsof thermocouple material up against the pipe directly. This solves mostof the problems of the plate, but is less rugged and more costly.

SUMMARY OF THE INVENTION

This invention provides a third thermocouple technique that usesthermocouple rails. Eliminating the plate and pressing thermocouplematerial (rails) up against the pipe directly provides a very fastresponse and an accurate reading. Its principle of operation is similarto that of the plate thermocouple device with the difference being theabsence of a plate.

The plate, the contact spots, the weld locations, and the distancebetween the welds and the contact spot cause all the problems with theplate design. The rail design according to the present inventioneliminates the problems associated with plate thermocouple devices bymaking the pipe itself the intermediary metal. The elegance of thepresent invention is that the contact spot is the thermal junction. Theelectrical junction that measures temperature is at exactly the sametemp as the contact spot, because they are the same spot. Readings aremuch faster and more accurate than can be obtained using priorabove-referenced thermocouple devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram showing the use of a prior artplate-type thermocouple device to measure the temperature of a pipe;

FIG. 2 is a functional block diagram showing the use of a thermocoupledevice according to the present invention to measure the temperature ofa pipe;

FIG. 3 illustrates a thermocouple device according to the presentinvention that includes a clamp and a thermocouple wire assemblyassociated with the clamp;

FIG. 4 illustrates half of the clamp of FIG. 3 with thermocouple wiresconnected to corresponding thermocouple rails;

FIG. 5 illustrates thermocouple wires from the thermocouple wireassembly connected to corresponding thermocouple rails;

FIG. 6 illustrates a thermocouple device according to the presentinvention being used with a small diameter pipe;

FIG. 7 illustrates a thermocouple device according to the presentinvention being used with a large diameter pipe;

FIG. 8 is a perspective view of a second embodiment of a thermocoupleclamp device according to the present invention that includes a pair ofthermocouple slats that comprise thermocouple contacts;

FIG. 9 is a perspective view of a pair of wires connected to thethermocouple slats of FIG. 8;

FIG. 10 is a side elevation view showing the thermocouple device of FIG.8 being used with a small diameter pipe;

FIG. 11 is a side elevation view showing the thermocouple device of FIG.8 being used with a large diameter pipe;

FIG. 12 is a perspective view showing the thermocouple device of FIG. 8showing the thermocouple slats spaced apart to form an open circuitconfiguration;

FIG. 13 s a perspective view showing the thermocouple device of FIG. 8showing the thermocouple slats spaced apart to form a closed circuitconfiguration; and

FIG. 14 is a perspective view showing the thermocouple slats in contactwith an electrical conductor.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a prior art thermocouple device 10 is arranged tomeasure the temperature of an electrically conducting pipe 12. Thethermocouple device 10 includes a first thermocouple wire 14 thatextends between a thermocouple 16 and a voltmeter adjustable 18. Thethermocouple 16 is connected to the underside (as seen in FIG. 1) of ametal plate 18 by any convenient means such as welding or soldering. Asecond thermocouple wire 20 extends between the voltmeter 18 and athermocouple 22 that is also connected to the underside of the metalplate 18. Temperature measurements using the thermocouple device 10involve exerting pressure on the plate 18 to bring the thermocouples 16and 22 into contact with the pipe 12. The temperature of the pipe 12 maythen be determined by the voltage difference between the twothermocouples 16 and 22.

FIG. 2 illustrates a thermocouple device 26 according to the presentinvention. A first thermocouple wire 28 extends between a thermocouple30 and a voltmeter 32. The thermocouple 30 is connected to a first rail34 that extends across the pipe 12. A second thermocouple wire 36extends between the voltmeter 32 and a thermocouple 38 that is connectedto a second rail 40 that is spaced apart from the rail 34. Thethermocouples 30 and 38 are formed of dissimilar metals. The rails 34and 40 are formed of the same metal as the corresponding thermocouples30 and 38. The thermocouple wires 28 and 36 are formed of the same metalas their corresponding rails 34 and 40.

FIGS. 3, 4, 6 and 7 show the thermocouple device 26 according to thepresent invention mounted in a pipe clamp 42 that includes clamp halves44 and 46. A thermocouple wire assembly 48 extends between the handlesof the pipe clamp 42 to a location between the clamp jaws.

As best shown in FIG. 5, the separate thermocouple wires 28 and 36extend out of the thermocouple wire assembly 48 and are connected to thethermocouples 30 and 38, respectively. The rails 34 and 40 may beparallel and arranged to extend transversely across the pipe 12.Alternatively, the rails 34 and 40 may be arranged such that spacebetween the ends 34 a and 40 a differs from the space between the ends34 b and 40 b. Having the rails 34 and 40 formed so that differentdistances between the corresponding ends are beneficial when the surfaceof the pipe 12 is dirty or corroded. The rails 34 and 40 may be placedin contact under pressure from the clamp 42 with the pipe 12. Rotatingthe clamp through a small angle about the pipe causes the rails 34 and40 to plough away material on the surface of the pipe 12 so that therails 34 and 40 and the thermocouples 32 and 38 make good thermalcontact with the pipe 12.

Bringing the rails 34 and 40 into thermal contact with the pipe 12creates two thermocouple junctions where each of the rails 34 and 40contacts the pipe 12. A voltage is produced between the thermocouplejunctions in accordance with the well-known thermoelectric effect. Thisvoltage is processed to determine the temperature of the pipe.

The rails 34 and 40 may arranged at an angle relative to one another sothat a wide range of pipe sizes may be measured using the samemechanical pivot style clamp 42 as shown in FIGS. 6 and 7. The angles ofthe rail 34 and 40 may be is such that the ends of the rails 34 and 40closest to the outer end of the clamp 42 are slanted so that the largestpipe size is still pushed to the ‘throat’ of the clamp (doesn't ‘spit’the pipe out). The inside end portions of the rails 34 and 40 are thenangled to push the smallest pipe towards the jaw opening (doesn't‘swallow’ the small pipe).

The rails 34 and 40 allow the pipe clamp 42 to be pulled toward the pipe12 as the clamp 12 applies pressure to the pipe 12. This enables theclamp to have both more stability and higher resistance to coming offthe pipe, or a lighter spring that is less expensive and easier to use.With the plate design, any ‘cocking’ of the installed pipe clamp indirection of the pipe causes the plate to be lifted off the pipe, withthe contact spot only on the edge, thermally far away from the junction.

Referring to FIGS. 8 and 9, a clamp thermocouple device 50 includes twothermocouple slats 62 and 64 of K-type thermocouple material havingwidths of about 5mm mounted in jaws 58 and 60. If a metal pipe (FIGS. 10and 11) is in the jaws 58 and 60 forming an electrical and thermalcontact to both slats 62 and 64, the two junctions create a voltage thatmay be read as a temperature. The difference between the thermocoupleclamp device 50 and the embodiment of the invention described withreference to FIGS. 3-7 is that the metal thermocouple contacts in thethermocouple device 50 extend from side to side (parallel to the pipe)instead of front to back (perpendicular to the pipe). A wire assembly 66includes thermocouple wires 67 and 68 that are connected to thethermocouple slats 62 and 64, respectively.

FIG. 12 is a perspective view showing the thermocouple device 50 of FIG.8 showing the thermocouple slats spaced apart to form an open circuitconfiguration.

FIG. 13 s a perspective view showing the thermocouple device 50 of FIG.8 showing the thermocouple slats 62 and 64 spaced apart to form a closedcircuit configuration.

FIG. 14 is a perspective view showing the thermocouple slats 62 and 64in contact with an electrical conductor.

What is claimed is:
 1. A thermocouple assembly for measuring thetemperature of a pipe, comprising: a pipe clamp; a first metal stripformed of a first metal mounted in the pipe clamp; a second metal stripformed of a second metal dissimilar to the first metal mounted in thepipe clamp; the first and second meal strips being arranged in the pipeclamp such that closing the pipe clamp on a pipe creates twothermocouple junctions where the metal strips contact the pipe; and athermocouple reading instrument connected to the metal strips toindicate the temperature of the pipe.
 2. The thermocouple assembly ofclaim 1 wherein the pipe clamp has a pair of opposing clamp jaws forgrasping a pipe and the first and second metal strips are mounted in aselected one of the clamp jaws.
 3. The thermocouple assembly of claim 2wherein the first and second metal strips are formed as spaced apartrails that are parallel to one another.
 4. The thermocouple assembly ofclaim 2 wherein the first and second metal strips are spaced apart andare arranged at an angle to one another with rails going from far apartto closer together to plow contaminants off the pipe and creating arobust thermal and electrical connection.
 5. The thermocouple assemblyof claim 1 wherein the pipe clamp has a first clamp jaw and a secondclamp jaw and the first metal strip is formed as a first slat mounted inthe first clamp jaw and the second metal strip is formed as a secondslat mounted in the second clamp such that the first and second mealstrips are on opposite sides of the pipe when a pipe is held between thefirst and second clamp jaws.